Preparation of agglomerate-free and highly crystalline (Ba0.5, Sr0.5)TiO3 nanoparticles by salt-assisted spray pyrolysis

Optimum conditions for the synthesis of non-agglomerated barium strontium titanate (BST) nanoparticles were examined. The effects of salt concentration, operating temperature, and droplet/particle residence time in the hot zone as a function of carrier gas flow rate and heating zones on particle size, crystallinity, and chemical composition of BST nanoparticles were investigated. Highly crystalline, dense BST nanoparticles in a size range of 17-60 nm with a narrow size distribution (sigma(g) = 1.2) were prepared using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing or for controlling of initial excess of barium and strontium in the solution, relative to titanium. The particle size decreased with decreasing salt concentration, operating temperature and droplet/particle residence time in the hot zones. The chemical homogeneity of the resulting particles was analyzed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The chemical composition of the resulting powder completely reflected the initial solution composition. SASP can be used to produce highly crystalline (Ba1-x, Sr-x) TiO3 (x = 0.5) nanoparticles in sizes as small as 30 nm in a single step.